An implantable medical device system typically comprises an implantable nerve stimulation system, an implantable cardiac stimulation system (known as cardiac pacemaker), and an implantable medication infusion system, where the implantable nerve stimulation system comprises a deep brain stimulation (DBS), an implantable cortical nerve stimulation (CNS), an implantable spinal cord stimulation (SCS), an implantable sacral nerve stimulation (SNS), and an implantable vagus nerve stimulation (VNS), etc.
For an example, the implantable deep brain stimulation system mainly comprises a pulse generator and lead implanted inside the body, and a control device outside the body, where the pulse generator is connected with the lead such that the pulse generated by the pulse generator is transmitted to the lead. The pulse generated by the pulse generator is delivered to particular nerve sites and restore the normal functionalities of the brain by means of electrical stimulation.
A clinician firstly determines the target in the patient's brain by means of a stereotactic surgery during the process of implantation operation. Then, the clinician drills a small hole in the patient's cranium and inserts a brain lead through the hole to the desired brain target site. The clinician uses a test stimulator to test the efficiency of the stimulation. If the effect of stimulating therapy is desirable, the brain lead is then anchored to the cranium using an anchoring device.
A device for anchoring a brain lead, described in the U.S. Pat. No. 4,328,813, typically comprises a socket and a plug. The plug is placed into the socket after the brain lead is inserted in the brain. The brain lead is secured by friction force between the socket and the plug.
However, the disadvantage of this method is obvious: the engagement between the plug and socket during the insertion inevitably brings the lead along with the plug's downward movement, thus causes the dislodgement of the electrodes from the desired stimulation site. Such dislodgement may result in unexpected clinical consequences. Moreover, the top portion of the plug sits over the flange portion of socket, which adds additional thickness to the device. Such thick foreign material on the cranium will cause discomfort or other complication to the patient.